A Phase 3 interventional study of PG4 Multivalent Vaccine and PG4 Multivalent Vaccine in Pneumococcal Disease, sponsored by Pfizer. Recruiting at 37 sites in United States. Open to participants aged 18 Years to 49 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-10-14.
Sponsored by Pfizer · Phase 3, Interventional, and Prevention
The purpose of this study is to provide safety data and demonstrate lot consistency with the PG4 vaccine by evaluating the immunogenicity of 3 different lots of this vaccine.
This study will compare a new pneumococcal vaccine with the vaccine currently in use to see if they are similarly safe. It will also compare three batches of the new vaccine to make sure they work the same way. Blood samples will be taken to measure how the body responds to the vaccines.
The study will be conducted in the United States. Participants will be assigned to 1 of 4 groups. Group 1: PG4 vaccine lot 1; Group 2: PG4 vaccine lot 2; Group 3: PG4 vaccine lot 3; Group 4: 20vPnC.
Within each group, participants will be assigned by chance in a 2:2:2:1 ratio to receive 1 vaccine injection (shot) with either PG4 (new vaccine) lot 1, PG4 lot 2, PG4 Lot 3 or 20vPnC, given in the arm. This means that for every 7 participants, about 2 will receive either PG4 lot 1, lot 2 or lot 3 and about 1 will receive 20vPnC.
Each participant will take part in the study for approximately 6 months.
298 studies on the registry are indexed under Pneumococcal Infections; 26 are open to participants now.
This study's planned enrollment of 4,670 is above the median of 373 across 253 interventional studies indexed under Pneumococcal Infections.
Browse Pneumococcal Infections studies →Pfizer is the lead sponsor of 3,334 studies on the registry; 149 are open to participants now.
Of its 601 completed or terminated interventional studies of FDA-regulated products, 391 (65%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Adults 18 through 49 years of age, who have no history of receiving a pneumococcal vaccine after 5 years of age.
Exclusion Criteria:
Individuals with a history of severe allergic reactions to a vaccine or its components, serious chronic medical disorders, significant psychiatric conditions, known or suspected immunodeficiency, substance abuse issues, asplenia, bleeding diathesis or prolonged bleeding, a history of a prior confirmed invasive pneumococcal infection, and pregnant or breastfeeding females will be excluded from enrollment in the trial.
Multivalent Pneumococcal Vaccine
Biological: PG4 Multivalent Vaccine
Multivalent Pneumococcal Vaccine
Biological: PG4 Multivalent Vaccine
Multivalent Pneumococcal Vaccine
Biological: PG4 Multivalent Vaccine
20 Valent Pneumococcal Conjugate Vaccine
Biological: 20 Valent Pneumococcal Conjugate Vaccine (20vPnC)
Multivalent Pneumococcal Vaccine
Also known as: PG4 lot 1
Multivalent Pneumococcal Vaccine
Also known as: PG4 Lot 2
Multivalent Pneumococcal Vaccine
Also known as: PG4 Lot 3
20 Valent Pneumococcal Conjugate Vaccine
Also known as: Prevnar 20
Percentage of Participants with Prespecified Local Reactions Within 7 Days After Vaccination
Prompted local reactions after each dose
Time frame: Within 7 days after Vaccination
Percentage of Participants reporting Prespecified Systemic Events Within 7 Days after Vaccination
Prompted systemic events after each dose
Time frame: Within 7 days after Vaccination
Percentage of Participants with Adverse Events (AEs)
AEs occurring from Dose 1 to 1 month after the vaccination
Time frame: From Vaccination to 1 month after Vaccination
Percentage of Participants with Serious Adverse Events (SAEs)
SAEs occurring from Dose 1 to 6 months after the vaccination
Time frame: From Vaccination to 6 months after Vaccination
OPA geometric mean ratios (GMR) between each pair of PG4 vaccine lots
OPA GMRs between each pair of PG4 vaccine lots at 1 month after vaccination
Time frame: 1 month after Vaccination
OPA Serotype-specific geometric mean titers (GMT) for PG4 vaccine serotypes
OPA GMTs at 1 month after vaccination
Time frame: 1 month after Vaccination
OPA geometric mean fold rise (GMFR) for PG4 vaccine serotypes
GMFRs in OPA titers from before to 1 month after vaccination
Time frame: From before vaccination to 1 month after vaccination
Percentages of participants with a ≥4-fold rise in opsonophagocytic activity (OPA) titers
Percentages of participants with a ≥4-fold rise in OPA titers from before to 1 month after vaccination
Time frame: From Vaccination to 6 months after Vaccination
Percentages of participants with OPA titers ≥ lower limit of quantitation (LLOQ)
Percentages of participants with OPA titers ≥ lower limit of quantitation (LLOQ) from before vaccination to 1 month after vaccination
Time frame: From before vaccination to 1 month after vaccination
Plan to share: Yes — Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.
Data sharing details ↗ · www.pfizer.com
Started Sep 2026 (actual). Primary completion is estimated for Jun 2027, 8 months after the start.
Of 81 industry-sponsored phase 3 interventional studies under Pneumococcal Infections, half reached primary completion within 13 months of starting (the median), counting those still running; a quarter within 9 and three quarters within 23. This study's planned 8 months is below that.
Counting every sponsor, half of 82 studies reached it within 13 months; a quarter within 9 and three quarters within 23.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
Contact study teamGet an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.